Heretofore, shaft couplings for inboard engine driven vessels have been utilized as a means of connecting shorter shaft end to end to span the distance between the transmission and the propeller, the shaft connected to the transmission being the main or driven shaft and the shaft connected to the propeller being the tail or drive shaft. In case of torsional overloading of the propulsion system, such as the propeller hitting a submerged object while under power, there have been no previous coupling designs that allow for the forced rotation of the shaft within the coupling without destroying the coupling body and the shafts being joined thereby subjecting the shafts and the coupling body to permanent damage if either shafts were to rotate within the coupling.
The present invention utilizes a replaceable sleeve between the coupling body and the shafts being joined. This feature makes this coupling field repairable, whereas the previous designs had to be replaced entirely. Another feature of this improved coupling is the method used to keep the shafts locked inside the coupling.
U.S. Pat. No. 3,583,356 to Milton T. Barker addresses the problem of the shaft pulling out of the coupling when the propulsion system was operated in reverse. Barker's solution was the addition of disks fastened to the ends of the shafts being joined. The immediate disadvantages of the discs are the additional machining required and the larger diameter coupling body necessary to accommodate the disks. It is possible that if either shaft were to rotate within the coupling, the screw attaching the disc to the shaft would loosen from the shaft rendering the disks ineffective in keeping the shaft within the coupling.
The improved coupling of the present invention utilizes the mounting screws to mate with a single circumferential groove, machined near the end of each shaft to be joined, to keep the shafts in the coupling should either shaft be forced to spin inside the coupling.